1. Field of the Invention
The present invention relates to a magnet type rodless cylinder of a type comprised of a piston arranged movably in the tube axial direction in a cylinder bore formed in a cylinder tube and a slide arranged movably in the tube axial direction at the outer circumference of the cylinder tube and magnetically coupling the piston and the slide, more particularly relates to a magnet type rodless cylinder wherein end caps connected at the two ends of the cylinder tube or the slide arranged at the outside of the cylinder are provided with external dampers.
2. Description of the Related Art
In the past, there has been known a slit type rodless cylinder of the type where a piston body and a slide arranged at the outside of the cylinder are connected integrally through a slit provided in the cylinder in the axial direction. In a slit type rodless cylinder, it is known that when the end caps connected to the two ends of the cylinder tube and the piston collide when the piston moves to the cylinder ends, the shock etc. are absorbed by attachment of various types of dampers at the end caps. As a slit type rodless cylinder provided with such dampers, there are the ones disclosed in for example Japanese Unexamined Patent Publication No. 10-318210 or Japanese Unexamined Patent Publication No. 11-13712.
On the other hand, as the rodless cylinder, as disclosed in for example Japanese Unexamined Utility Model Publication No. 7-28403, there is known a magnet type rodless cylinder magnetically coupling a piston housed in a cylinder tube and a slide arranged at the outside of the cylinder tube utilizing magnets.
Here, the configuration of dampers of the slit type rodless cylinder disclosed in Japanese Unexamined Patent Publication No. 10-318210 will be explained with reference to FIG. 8. FIG. 8 is a partial cross-sectional view of a slit type rodless cylinder 71. The slit type rodless cylinder 71 is configured by a cylinder tube 72 provided with a not shown slit and in which a piston 73 is arranged movably in the axial direction of the cylinder tube 72. Part of the piston 73 is extended through the slit to the outside of the cylinder tube 72. This extended part is formed as a slide 74 at the outside of the cylinder tube 72. At the top surface of the slide 74 is attached a connection mount 75 guided by a guide rail 76. A workpiece etc. is placed on the connection mount 75.
Further, end caps 77 are connected to the two ends of the cylinder tube 72 (in FIG. 8, only the left end shown). Between the end caps 77 and piston 73, cylinder chambers 78 are formed at the two sides of the piston 73. By supplying fluid to the cylinder chambers 78, the piston 73 and the slide 74 and the connection mount 75 integrally formed with this move in the cylinder axial direction. The shock due to the collision of the end caps 77 and piston 73 when the piston 73 moves to the ends of the cylinder tube is absorbed by providing the end caps 77 with internal dampers 79.
On the other hand, the slit type rodless cylinder disclosed in Japanese Unexamined Patent Publication No. 11-13712 has substantially the same configuration as the slit type rodless cylinder 71 of Japanese Unexamined Patent Publication No. 10-318210, but the end caps are provided with not only internal dampers arranged inside the cylinder tube to absorb the shock of collision of the piston, but also external dampers arranged at the outside of the cylinder tube for absorbing the shock of collision with the slide. Further, the slit type rodless cylinder of Japanese Unexamined Patent Publication No. 11-13712 is of a type not using any connection mount. The external dampers and internal dampers simultaneously absorb the shock due to collision of the slide and piston with the end caps.
Further, the magnet type rodless cylinder 81 disclosed in Japanese Unexamined Utility Model Publication No. 7-28403 will be explained with reference to FIG. 9. FIG. 9 is a partial view of the magnet type rodless cylinder 81 disclosed in Japanese Unexamined Utility Model Publication No. 7-28403. The magnet type rodless cylinder 81 disclosed in Japanese Unexamined Utility Model Publication No. 7-28403 is provided with the same configuration as the conventional generally known one. That is, the magnet type rodless cylinder 81 is configured arranging in a cylinder tube 82 a piston having inside magnets (not shown) and movable in the axial direction of the cylinder tube 82, arranging a slide 84 having outside magnets at the outside of the cylinder tube 82, and magnetically coupling the piston and slide by the magnets across the wall surface of the cylinder tube 82. Due to this, by making the piston move in the cylinder tube 82, the slide 84 magnetically coupled with the piston moves along with the piston in the axial direction of the cylinder tube 82. The two ends of the cylinder tube 82 are provided with end caps (not shown). The slide 84 and piston are designed to be movable inside and outside of the cylinder tube 82 up to the end cap positions. Further, on the top surface of the slide 84, a connection mount 85 is attached through connecting hardware 88. The connection mount 85 is guided by a guide rail 86.
However, in the general magnet type rodless cylinder shown in Japanese Unexamined Utility Model Publication No. 7-28403, sometimes distinctive problems occur when the piston or slide stops due to striking/contacting the end caps. In a magnet type rodless cylinder, the piston and slide are not mechanically coupled, but are only magnetically coupled. For this reason, when the piston and slide move to a position striking/contacting an end cap and stop, if the inertial energy of the piston and slide causes positional deviation between the piston and slide, sometimes the magnetic coupling of the piston and slide ends up being lost. In particular, if providing a connection mount on the slide, when the connection mount strikes/contacts an end cap, the slide stops at a position separate from the end cap by exactly the amount of projection of the connection mount from the slide (that is, the connection mount first ends up striking/contacting the end cap, so the slide cannot move to its inherent striking/contacting position). Therefore, in this case, the problem arises that the piston ends up moving to a position striking/contacting the end cap against the magnetic coupling force due to its inertia and the magnetic coupling is easily lost.
Further, in the magnet type rodless cylinder disclosed in Japanese Examined Utility Model Publication No. 7-28403, assembly work of the connection mount is very burdensome and it is difficult to satisfy the requirement of the users such as attaching and detaching the connection mount in accordance with the size and kind of the works. Therefore, there has been a long time need for a magnet type rodless cylinder in which a connection mount can be attached or detached easily and is able to prevent disconnection of the magnet coupling between the piston and slide even when a connection mount is attached to the slide.
Therefore, as disclosed in Japanese Unexamined Patent Publication No. 10-318210 and Japanese Unexamined Patent Publication No. 11-13712, in a slit type rodless cylinder, various types of dampers are known. However, it should be noted that a slit type rodless cylinder and a magnet type rodless cylinder largely differ in purpose of attaching the dampers. That is, in a slit type rodless cylinder, since the piston and slide are formed as a single member, at the time of stopping, the positional deviation between the piston and slide does not cause the magnetic coupling to be lost. For this reason, in a slit type rodless cylinder, the dampers are only for absorbing impact at the time of collision of the slide and end caps. Therefore, if using such dampers as they are for a magnet type rodless cylinder, when for example the set external dampers are too large, the deviation between the striking/contacting position of the piston and the stopping position of the slide ends up becoming further larger and the above problem sometimes ends up being further aggravated.